PracticalDermatology

Dubbed the “Sunshine vitamin” because the human body synthesizes it in response to UVA exposure, vitamin D’s pleasant moniker could also be ascribed to reduced rates of depression and cognitive impairment seen in those with high levels of vitamin D. Conversely, low rates of vitamin D are associated with osteopenia and osteoporosis, cancer (especially colorectal cancer), heart disease, hypertension, diabetes, and age-related macular degeneration.¹

Vitamin D deficiency has been termed a “pandemic,” as accumulated evidence over the last decade or more has confirmed that more than one billion individuals worldwide may have vitamin D insufficiency or deficiency.² Some have argued—often vocally—that one contributing factor to vitamin D insufficiency is UV avoidance and increased sunscreen use over the past several years. In fact, some have argued in favor of purposeful UV exposure with the goal of increasing vitamin D synthesis. Clinical Practice Guidelines from the Endocrine Society cite sunscreen use as a possible contributor to reduced vitamin D synthesis but do not belabor the point.³ Of note, the guidelines recommend use of vitamin D supplements in patients with vitamin D insufficiency and do not advocate UV exposure as a “treatment.” Nonetheless, controversy over the extent of vitamin D insufficiency in the US, implications for UV safety, and the need for supplementation has led to some confusion in the general public. New research provides compelling evidence that use of SPF does not dramatically interfere with vitamin D synthesis.⁴

The Latest Findings

Researchers recently assessed the impact of sunscreen use on vitamin D synthesis among healthy volunteers. The specifics are a bit complex, however the top-line data tell the story. Subjects on a weeklong holiday in a sunny locale were provided either a sunscreen with SPF 15 and high UVA protection factor or a sunscreen with SPF 15 and low UVA protection factor and agreed to use it as directed on a daily basis. All subjects were advised on appropriate sunscreen application in terms of amount and frequency of application. A third group of holiday-takers was advised on sunscreen (SPF 15) application but instructed to use it at their discretion. Sunscreen use in all groups was assessed on a continuous basis. Serum samples were collected from all subjects 24 hours before and 24-48 hours after the week-long holiday. Baseline and post-holiday erythema were also assessed.

Various statistical analyses showed highly significant increases in serum values of 25(OH)D3 from baseline among all subjects in the holiday groups. There was no statistically significant difference in serum vitamin D for the low UVA protection factor and high UVA protection factor holiday groups in the post-holiday assessment, indicating that high UVA protection factor did not inhibit vitamin D synthesis compared to low UVA protection factor. There were no significant changes in erythema values from baseline in either group, indicating that patients had adequate UV protection with the sunscreen regimen. The group of discretionary sunscreen users had higher post-holiday serum vitamin D values relative to the other two groups, and there was an increase in erythema from baseline in this group.

The authors conclude based on their real-life study that, “typical use of high SPF sunscreens probably has a limited impact on vitamin D synthesis.”

A Powerful Message for Patients

This is not the first study to suggest that proper use of SPF does not dramatically inhibit vitamin D synthesis, however, it is a well-designed, “real-world” study that adds significantly to the argument in favor of SPF use. Many times we may find ourselves telling patients, “there is no evidence” of a particular sunscreen effect. Now we can use this data to rephrase the message more powerfully: There is evidence that sunscreen use appears to not interfere with vitamin D synthesis.

Patients concerned about vitamin D insufficiency should consider supplementation, seek guidance from a GP or endocrinologist on additional measures to increase and monitor serum vitamin D levels, and apply sunscreen according to the package label on a daily basis—even during these winter months.

1. Nair R, Maseeh A. Vitamin D: The “sunshine” vitamin. J Pharmacol Pharmacother. 2012 Apr;3(2):118-26.

2. Holick MF. The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Rev Endocr Metab Disord. 2017 Jun;18(2):153-165.

3. Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM; Endocrine Society. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30.

4. Young AR, Narbutt J, Harrison GI, Lawrence KP, Bell M, O’Connor C, Olsen P, Grys K, Baczynska KA, Rogowski-Tylman M, Wulf HC, Lesiak A, Philipsen PA. Optimal sunscreen use, during a sun holiday with a very high ultraviolet index, allows vitamin D synthesis without sunburn. Br J Dermatol. 2019 Nov;181(5):1052-1062.